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Branch of biology which deals with the study of microscopic organisms. Bacteria, virus, protozoans all are microscopic organisms.

Microorganisms are associated variety of ways with the food we eat. They may spoil the availability and even quantity of our food.

It is necessary to protect food from microbial contamination and spoilage. Food material can also be preserved by following methods.

1. Prevention of contamination.
2. Killing of microorganisms.
3. Prevention of microbial growth. Slowing down metabolism.

Contamination by microbes can be prevented by preparing food and handling it in hygienic germ free environment.

Many microorganisms can be killed by treating bacteria with high temperature. Ionizing radiations are also used to kill microorganisms.

Microorganisms and most of the spores are killed within 5-10 minutes by boiling.

This form of heat is used in a pressure cooker. Microorganisms can be killed within 10-15 minutes using different steam pressure.

It is done by heating milk at 62.8° C for half hour or heating at 71.7° C for 15 seconds in specially designed equipment. Pasteurized milk should be kept in refrigerator.

In this method, milk, fruit juices and other food products are heated at 148.9° C for 1 to 2 seconds to kill microorganisms and spores.

Radiation such as gamma rays and cathode rays are used for commercial sterilization of food. They kill microorganisms at room temperature.

Growth ant metabolism can be retarded by various means.

Temperature near 0° C and lower retard the growth and metabolism of microorganisms. They are not killed. Refrigerators are used for this purpose.

Drying food in sun or by applying heat causes dehydration. Due to the lack of water, microorganisms cannot grow.

Food can be preserved by the addition of certain chemicals such as benzoic acid, lactic acid and acetic acid. At low pH bacteria cannot grow.

Microorganisms not only spoil the food but also other products like paper and textiles and thus cause great loss. They produce slime on paper, stain or disodour it and leaken its fibers.

Another example is spoilage of cotton wool and ropes by microorganisms.

Tuberculosis is infectious disease and is caused by a germ mycobacterium tuberculosis.

Germs of this disease may attack lungs, intestine or bones.

Person suffering from this disease can transfer germs of disease to another person by sneezing, spitting, and expiration. Germs of this disease can also be transferred by infected food.

1. Slight fever
2. Loss of weight
3. Prolong and continuous cough

1. General health should be improved so that the immunity of the body may increase.
2. Environment should be hygienic.
3. A person suffering from this disease should be admitted in sanitarium.
4. Milk should be used after boiling.
5. The sputum of patient should be burnt.

It is an acute infectious disease caused by bacterium salmonella typhosa.

Patient suffer from contained high fever, headache and inflammation of intestine.

The germ of this disease enter the intestine of human body along with food and water.

It is very serious infectious disease of digestive tract caused by bacterium vibro comma.

The bacteria can be transmitted by contact with water and by food contaminated with faeces from cholera patients.

The incubation period of vibro comma varies from few hours to about days. Vomiting and profuse diarrhea type of motions are typical symptoms of this disease causing dehydration, loss of minerals and increased acidity of the blood of patient. Severe attacks may even lead to death in 2-3 days.

1. Water and food stuff should be clean.
2. Faeces of the patient shoulf be properly disposed off to prevent the spread of disease.

This is a disease of

It is caused by specie of shigella.

The bacteria enters the human being via contaminated food and water.

1. The stool contain blood, mucus and pus.
2. Sometimes patients get fever.

Disease can be controlled by improving personal hygienic, sanitation, proper sewage disposal and fly control.

Tetanus is caused by bacterium called clostridium tetani.

The spores of bacteria enter through wounds, bruises, umbilical stumps of new born baby. If the conditions are favourable that is anaerobic conditions these spores germinate and produce a toxin. The toxin affect the central nervous system and violent contraction of body muscles when the muscles of jaw are affected the mouth cannot be opened.

Death results from respiratory failure.

1. Tetanus antitoxin is given to the patient.
2. Penicillin is given to stop the growth of bacteria.
3. Tetanus is controlled by immunizing people with vaccine.

It is also known as infantilo paralysis.

This disease is caused by polio virus.

The virus enter the digestive tract through the mouth. From where it penetrate the blood vessels and finally reaches the nervous system, where it destroy the nerve cells and cause paralysis.

1. Common cold accompanied by fever, headache.
2. Indigestion and also vomiting, stiffness of neck and back.
3. Paralysis and spasm of muscles.

1. Patient should be isolated and hospitalized.
2. Faeces and discharge of nose and throat should be disinfected.
3. Children should immunized against this disease with polio vaccines.

It is caused by virus which enter the human body through respiratory tract.

When the virus enter into the blood stream it cause cough, headache and inflammation of eye.

1. Spots in mouth are present several days before the rash come out.
2. The rash of measles consist of pink brownish blotches spread all over the body.

There is no specific treatment for measles. Antibiotics are often used to prevent secondary complication.

It is a disease of skin and nails.

It is caused by fungus belonging to the dermatophytes group. The disease spread by direct person to person contact or by infected objects like towels. Some fungal infections are spread by animals such as cat and dogs.

1. Toes get infected and there is itching between the toes.
2. The skin starts peeling and cracking.
3. The nails get infected becoming yellow, thick and brittle.

1. Keep the feet dry.
2. A physician should be consulted.

This is an infection caused by a group of fungi belonging to the genus trichophyton. The fungi causing this disease are collectively known as dermatophytes.

The fungi on attacking the skin cause localized lesions in the skin. Lesions assume circular form. Some dermatophytes infect the hair follicles, hairs and nails.

It can be cared by external application of certain fungicide ointments.

Malaria is the disease caused by protozoan called plasmodium. It is transferred into human blood by mosquitoes.

1. Patient feels very cold.
2. Body temperature is above 37° C.
3. Attack is accompanied by nausea and headache.

This disease can be prevented by spraying kerosene oil and DDT on top of the water to kill mosquitoes.

This disease is treated by Quinine.

There are many useful applications of microorganisms.

1. Microorganisms are used for production of yogurt, cheese, pickles, beer and wine.
2. Many antibiotics are obtained from some microorganisms for the treatment of disease. E.g., penicillium streptomycin.
3. They are used in production of vaccines.
4. Some of the organisms produce vitamin B₁₂.
5. They increase soil fertility.
6. They decompose dead organic matter.
7. Some bacteria are used to produce hormones as human insulin.
8. Microorganisms are used to produce antibodies on commercial scale for specific disease such as cancer.

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